Brief encounter

 作者:谷梁峋惴     |      日期:2019-03-08 01:11:05
By Jeff Hecht THE world is going to end in 2028—or so we thought in March. Asteroid hunters are still soothing ruffled feathers after reports that asteroid 1997 XF11, a lump of rock between 1 and 2 kilometres across, might hit the Earth in 2028. The resulting furore persuaded astronomers to revise their procedures to avoid further debacles. The March warning began with an electronic circular from Brian Marsden of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. He noted that preliminary calculations showed a close approach and a remote possibility of an impact, and asked for more observations to help refine the orbit. Reporters quickly picked up on the apocalyptic story, and were soon swarming around Marsden’s office. Then NASA moved to ease fears, announcing that Don Yeomans of the Jet Propulsion Laboratory (JPL) in Pasadena had calculated there was no chance of impact in 2028. The case was closed within hours, after Eleanor Helin of JPL found a previously unrecognised 1990 image of 1997 XF11, which confirmed that it would miss Earth. As the dust settled, astronomers agreed not to go public with impact warnings until others have confirmed their calculations and checked for old observations that could help refine predictions. NASA has also put Yeomans in charge of a new office to coordinate asteroid searches. One thing is sure, says Rick Binzel, an astronomer at the Massachusetts Institute of Technology in Cambridge: “Everyone will be much more careful the next time.” More on these topics: